


Mind the tail, bro!

by xyChaoticFox



Category: Ao no Exorcist | Blue Exorcist
Genre: Don't Like Don't Read, Fluff and Smut, M/M, Masturbation, Sexual Relationship, Sexual Tension, Sibling Incest, Tail Kink, Yaoi, biting kink
Language: English
Status: Completed
Published: 2015-11-23
Updated: 2016-03-07
Packaged: 2018-05-03 01:11:05
Rating: Mature
Warnings: Underage
Chapters: 4
Words: 3,641
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5270942
Author URL: https://archiveofourown.org/users/xyChaoticFox/pseuds/xyChaoticFox
Summary: <blockquote class="userstuff">
              <p>Rin discovers something new about his tail in the most awkward and thrilling way.</p>
            </blockquote>





	1. Control that thing: Part 1, Discovery

**Author's Note:**

> Please excuse the errors, this is not beta'd or edited. Leave any comments or thoughts. :) Tips are welcome and appreciated. P.S English is not my first language.
> 
> Disclaimer: I do not own the characters, only the plot. :D
> 
> ~☆~
> 
> ◈Please don't be shy and talk to me. ◈

Yukio's brow twitched in aggitation when he feels another flick at his back. Glaring from underneath his dark lashes, he stared at his twin's twitching tail. His eyes move to Rin's face to see if he was playing again, but the older was actually trying to concentrate on the assignment before them. He scoffed silently, hoping Rin wasn't playing some stupid game with him again. With one more glance at the swaying tail, he focused back on his own work. The half demon's tail has been bothering him for the last thirty minutes. 

 

It brushed against the hair at the back of his head, flicked at his thigh, grazed his ear or poked his shoulder. They were suppose to be studying, it was Rin's own fault for slacking. He just had to stay in on a Friday and finish all his assignments. Atleast he wasn't complaining anymore like he did the first two hours, but his damned tail wouldn't stop! Finally Yukio burst, slamming his fist against the table, making his brother jolt. 

 

"Could you stop!" he scolded. 

 

"What? Homework? Anytime." he grinned and closed his book. 

 

"No, idiot. Your tail." He stated pointing at it. 

 

"What about it?" Rin peered over his shoulder at the moving appendage. 

 

"Control it! It keeps on touching me and it's getting irritating." 

 

Before Rin could reply the tail striked again, sending Yukio's glasses falling to the floor, fortunately not damaging them in the process. Yukio gave a frustrated growl and Rin couldn't hold back his laugh anymore. 

 

"I-I'm so-rry," he spewed between bubbles laughter, "The thing has a m-mind of its own!" 

 

Yukio glared at him before turning away again. He gripped his pen, trying to continue. Still having small puffs of laughter, Rin tried to continue as well. Not long and the silky appendage flicked again. With another frustrated cry, Yukio grabbed the dark tail. Rin almost choked as his head shot up in a shocked hiss. Yukio's mouth moved but Rin heard nothing as the fingers flexed around the soft fur. He shuddered, surpressing another shiver down his spine and trying not to move or alert Yukio of his new and pleasurable discovery.

~~


	2. Control that thing: Part 2 ,Interesting...

**Notes for the Chapter:**

> Tiny update.
> 
> Enjoy~

Rin chewed his bottom lip, eyes worriedly darting around the dark room. The pale moon light streamed through the slightly drawn curtains and illuminated the figure opposite him. Even with the ounce of light provided, he wasn't sure if his brother was sleeping and it made him even more uncomfortable. Yukio was motionless except for occasional shifting as he inhaled and exhaled.

 

With his breaths steadily paced, he was probably asleep but you couldn't be too sure. Yukio suddenly moved, throwing his blanket off and muttering something while his hands gripped the sheets. You see what he meant? Rin bit harder into his bruised lip, shifting his gaze to his lap.

 

 He sat on his bed, legs dangling over the side and knees pressed securely against each other. He rubbed them together, trying to calm down but it had quite the opposite effect. His cheeks flushed further and the unsettling arousal in the pit of his stomach intensified. 

 

Yukio streched much like a cat would, resting on his stomache with one leg slightly pulled towards his chest. His cheeks were dusted with pink, his brows furrowed and tiny droplets ran along his cheek and jaw. It was pretty hot tonight and that made Rin even more upset. 

 

'Damn tail.' Yukio muttered, his leg hiking up even more.

 

The night shirt the younger wore, hitched up and revealed a smooth expanse of deliciously bumpy porcelain skin. Damn it, Rin didn't notice those muscles before! To make matters worse, his tail decided to come and play as well; rubbing itself along Rin's shoulder and side. This is all your fault, Rin thought bitterly as he glared at the oblivious twin.

 

Slowly his hips rose from the bed and he slipped his pants over creamy thighs. Keeping a eye out for Yukio, Rin let his hand slip into his boxers and prayed to anyone listening to keep his brother from waking. His fingers grazed his heated flesh and he clenched his lips shut, successfully trapping the noises in his throat.

 

Slowly they danced further before wrapping themselves around him in an urgent grasp. His other hand caught onto his tail and another lewd sound threatened to come out. His eyes flew open and his heart stopped, focusing on Yukio as fast as he could. He was still sleeping. Rin barely remembered his eyes closing. Did he even close them? 

 

His mouth opened in a silent gasp as his hand slid up and down, eyes widening and brows twitching at the tainted pleasure. This was something really....really new to him. He felt over-welmed and his pace quickened but he couldn't finish. Rin fell backwards, cool sheets embracing him and adding to his fantasies. He could imagine Yukio laying like that, caught in his cool sheets as sweat covered them in the throws of lust.

 

"Interesting." 

 

Rin's eyes opened and he shot upright, knocking Yukio over. 

 

"Y-Yukio!" 

 

He was flustered and caught with his hand literally inside his pants while he yearned for his brother. Yukio scoffed and pulled himself off the floor and onto the bed. He leaned over and inspected Rin's lap. 

 

"Don't s-stare at me, damn four e-eyes!" he exclaimed.

 

"Your tail is giving you sexual pleasure." Yukio hummed as if it was some new science discovery.

 

"S-shut up. Go away!"

 

"No need to get rude, you are the one masturbating with your brother next to you."

 

"You were asleep!" 

 

"Exactly. I was."

 

Rin blushed and was about to push Yukio away but a hand around his jaw stopped him. Yukio yanked him closer, mouth bruisingly crushing against his. He climbed into Rin's lap, behind pushing down on the straining and hard member. Rin gripped Yukio's hips, fingers digging into the skin as Yukio's slender fingers slid over his shoulders and into the long hair at the back of his neck. He yanked it, pulling Rin away and the elder hissed frustratingly. 

 

"Nii-san." Yukio's voice was firm and commanding.

It sent dangerous and forbidden shivers down Rin's arched spine. 

~~


	3. Who is in control?

**Summary for the Chapter:**

> Did it even happen?

**Notes for the Chapter:**

> A quick update~ I did not forget this story! With the last chapters I made a huge mistake with Japanese titles and I feel so stupid for not noticing when I actually used them correctly in another story. So sorry babies! I don't have much time but I decided to write a small piece and changed the story to 4 chapters. I'm finishing old stories before I write new ones/ continue with others.  
> Enough blabbing now, read on and I hope you like it :) ~

\--  
_“Niiiii-san.”_

_Rin hummed, back arching as he stretched._

_“Nii-san.”_

_“Yuki.”_

_“Nii-san!”_

_“Hmmm”_

“Rin!”

Rin jolted awake, coming face to face with a fuming Yukio. For a moment they just stared at each other before Rin’s ears tinted red and his face flushed, memories from last night surfacing. His right hand flew to his face, the back of it pressing against his mouth. Yukio didn’t flinch; no reaction what-so-ever , just blank frustration and disappointment.

“Listen, you better get your ass up and get to school. I swear, you really need to start getting your things straight.” Yukio pushed his glasses up his nose.

Rin watched with wide eyes as his brother got up, grabbing an armful of books and a loose pencil as he hurried out. Yukio didn’t say anything as he went downstairs, leaving Rin staring at the empty room and listening to the vibration and thudding of fading footsteps. He blinked, twisting his hand around to touch his lips. Slowly his fingers traced them; his mind almost replaying the scene that he swore took place the night before. He swallowed, lifting the covers of his bed but finding his body perfectly clean and fully clothed.

Did he not go against all the rules / reason and sleep with his little brother?

“Ehh, what the hell is going on?” Rin scratched the back of his neck.

He could still feel Yukio’s fingers curling between the thick strands and pulling at them until the skin underneath hurt like a bitch. Rin slid out of bed, hissing and bending over as his back and behind protested out in pain. His muscles flinched, tensing and pulling as he cursed and hopped around the room clutching his lower back.

“Damn it!” He rubbed harder, suddenly feeling quite bitter.

He stumbled pass Yukio’s bed, eyeing the neat sheets as he made his way to the bathroom. He struggled to pull his shirt off for a quick shower before school, cringing as his fingers tugged at the fabric and yanked it over his head. It was discarded on the floor as he eyed his reflection in the mirror and his mouth pulled into an unsightly grimace. He clutched at the sink, almost breaking it as he looked closer before stepping away, hands hovering close to his body. With a deep frown he traced the light marks scattered over his hip bones and abdomen. _Fingerprints_.

“Bitch!”

\--

“Did you see him?”

“I just told you-”

“I know! But I asked did you seeeee him, like, now?”

Shima shook his head, “Just this morning. He was in a bad mood so I just decided to nooot go there at all, man.”

Rin groaned, flinging his bag over his shoulder.

“You okay?

“Just fucking perfect!” Rin stomped away.

“Tch, dunno why his panties are all up in a bunch. Probably forgot homework again.” Shima scoffed, stuffing his mouth with candy bars.

\--

“Not since this morning, no. Yuki was pretty upset, is he okay?” Shiemi pouted.

Rin waved a dismissive hand at her and hurried away again, beyond any level of frustration at this point. His body ached, uncomfortably hot and attentive, all thanks to that damn four-eyes and now he just had to disappear without a trace. Rin’s knees rubbed against each other as he hurried into a bathroom-stall, sliding down against the cool tiles and letting his head fall back. His fingers clenched into fists and he bit his lip, trying to avoid his hormonal problem with all his power.What was all this crap? Did last night really happen or was he just having one hell of a realistic wet dream? His head thudded against the wall and he eyes closed.

_Rin’s head hit the back of the bed, a hand tightly wrapped around the underside of his jaw and around his neck. Yukio’s mouth covered his, trying to distract him from the hands trailing down his body and digging into his skin. His kiss was fierce and demanding, very much unlike Yukio and filled with a ravenous hunger. Teeth nipped at his bottom lip, pulling and sucking as his lip was pulled into Yukio’s mouth. He arched when hands grabbed hold of his hips and he was roughly and crudely pinned down. His bones creaked and groaned beneath his skin at the delicious pain filling him._

  
_His body was on fire, skin flushed and wet, burning fingers adding fuel to the fire as they dug into his skin. Yukio’s lean fingers slipped past the waistband of his underwear and grazed the flush skin, firmly gripping it and leaving Rin a whimpering mess. Teeth sunk into the thin skin of his neck, marking him over and over again, while his mouth opened to splutter out senseless pleas and begs to his brother. Thrilling, painful, tainted and pure bliss._

“Rin?”

Rin snapped out of his vivid day dream, pants wet and uncomfortable, “What?”

“It’s Shima, Yukio was looking for you too so I told him you wanted to see him,” Shima paused and continued when Rin didn’t reply, “I think Shiemi also spoke to him.”

“Oh, crap. Crap, crap, crap.”

“Something wrong?”

“No! Thanks, be out in a sec.” Rin rubbed his face, shaking his head.

\--

“You’re quiet.” Yukio pointed out as he pushed his plate forward.

“Yeah…” Rin muttered, avoiding Yukio’s eyes as he filled Yukio’s plate with steaming pasta.

“I heard you were looking for me.”

Rin nodded, moving to fill his own plate and chewing the inside of his cheek. His hands were sweaty and shaking, heart pulsing in his throat and anxiousness taking over. Yukio moved; brushing passed him to get glasses and soda. Rin swallowed, ignoring all the hairs that sprung up with electricity. He plopped down in his seat, keeping his eyes on his food and ignoring the other.

“Want some?”

“Yeah.”

He listened to the bubbly sound of his favourite soda as it hit the bottom of a glass and swirled around. Uneasily he tapped the table top with his forefinger, waiting for Yukio to place the glass next to him. He quietly thanked him and dug into his meal, trying to push his nausea down with the enormous amount of food. Yukio didn’t say anything but Rin could feel the fleeting looks in his direction and the ‘accidental’ brush of their knees beneath the table. What a… _lovely_ dinner. Yukio finished only half, getting up from the table to put away the leftovers and drop his plate in the sink, leaving the room with a speedy pace. Rin didn’t miss the tense muscles of his shoulders and the clenched jaw.

Rin struggled to swallow the last of his food, switching to a much slower pace than before. His ears strained, following the clear, rhythmic padding of sock clothed feet and the sound of the shower being turned on. He swallowed thickly, pushing his plate away and getting up with a scoff. He decided to leave his dirty dishes and hurry to bed, possibly the best way to avoid Yukio and a very uncomfortable conversation. Rin pulled his shirt off, dropping it in a laundry hamper and sneaking towards his bed.

“Rin! Could you bring me a towel?”

God damn it! How the hell did he now?

Rin’s teeth ground against each other as he grabbed a blue piece of material. He hesitated at the bathroom door, opting to rather just stick his arm in and tossing the towel to Yukio.

“Here.”

The door flew open, fingers wounding around Rin’s wrist and yanking him forward. His eyes blurred, the world spinning as his body connected with the icy wall. Yukio’s mouth pressed close to his ear, his body moulding against Rin’s own. His breath ghosted across Rin’s cheek and the elder shuddered, completely frozen from the sudden change.

Yukio’s lips brushed the sensitive skin of his lobe, “You’ve been thinking about it the whole day, haven’t you, _nii-san_?”

~~

 

**Notes for the Chapter:**

> The time skips and here&there pieces bothered me, but at least it's an update. I'll redeem myself with the last chappie. :D If this is a bit confusing, please feel free to shout at me to shine light on a few things. xD


	4. Blood is thicker than water.

**Notes for the Chapter:**

> This is the end, mien babies. 
> 
> Warning: ended up with some blood kink =.=

\-- 

The door flew open, fingers wounding around Rin’s wrist and yanking him forward. His eyes blurred, the world spinning as his body connected with the icy wall. Yukio’s mouth pressed close to his ear, his body moulding against Rin’s own. His breath ghosted across Rin’s cheek and the elder shuddered, completely frozen from the sudden change. 

Yukio’s lips brushed the sensitive skin of his lobe, “You’ve been thinking about it the whole day, haven’t you, _nii-san_?”

\--

“H-ha…nnh.” 

Rin’s back arched, fingers twisting into Yukio’s bed sheets and bunching the fabric in his hands. He clenched his jaw, biting down on his teeth and squeezing his eyes shut.

“Here, nii-san?” 

Yukio’s fingers slowly trailed over the base of Rin’s tail, gently stroking it and allowing his digits to wrap around it. Almost lazily his hand moved up along the twitching appendage, allowing it to wrap around his hand and arm as he followed its curves. He felt Rin shudder and saw the small tremors running through him, smiling with unabashed amusement. Yukio hovered above Rin’s back, leaning forward to whisper closely in the elder’s ear when he didn’t answer.

“Speak up, nii-san.”

Rin shook his head, smothering his heated face in the cool fabric. His knuckles turned white, tightening their grip and his body stretched, yearning Yukio’s touch when it disappeared. Yukio sat back on his haunches, his eyes carefully regarding the other. Rin turned to look over his shoulder, glaring more than actually looking and breathing heavily. He pushed himself up, trying to sit back as well and mimic Yukio’s position.

“You know, you don’t have to be a dick and leave me hanging.” He ran a hand through his hair and pushed the wet locks away from his forehead.

“And you can tell me what you want, Rin. Unlike you, I can’t smell hormones or whatever the hell it is you believe you smell.” Yukio said calmly, no bite in his tone.

“I think you know exactly what I want, _brother_.”

“But I want you to say it.” 

Rin’s hands dug into his jean covered thighs and he scoffed, “Yukio, I’m turned on and you started this.”

“May I remind you about why I started after the whole masturbati-”

“No!” Rin snapped, covering his face.

Yukio tilted his head to the side, focusing on the small drops of sweat at the back of Rin’s bare neck. He had an awful feeling like he wanted to lick it all up.

“Rin, turn around.”

Rin didn’t budge, shoulders tensing in response and showing his known stubbornness.

“God, why do you have to act like such a child?” 

Yukio grabbed Rin’s head, tugging him back with a bit more force than what was necessary. Rin fell back against Yukio’s naked chest, head falling on his shoulder and their cheeks brushed for a split second before Yukio turned his head. Yukio’s mouth harshly pressed down on Rin’s, the hand in his hair keeping him in place; locked between Yukio’s neck and shoulder. Rin’s arms lifted, a hand covering Yukio’s in his hair and the other cupping the back of Yukio’s neck. He leaned back further, tilting his head and opening his mouth to deepen their kiss.

Yukio chuckled into his mouth, slowly slipping his tongue inside the wet and waiting warmth. His tongue ran over the edges of Rin’s sharp teeth, one accidently cutting into him and their mouths tasted of copper. Rin moaned, enjoying the taste and trying to get more of it by suckling Yukio’s tongue. Yukio made a low sound at the back of his throat and pushed forward, giving a sharp tug to Rin’s head. Two slick muscles clashed and fought for dominance, the kiss quickly turning messy and hungry. Teeth clashed, lips smacked and tongues tangled, saliva slipping out and running slowly over their lips. 

Yukio’s free hand, which held one of Rin’s biceps, moved to Rin’s chest. His blunt nails traced invisible patterns and shapes, distracting Rin quite a great deal. His fingers danced over the flushed and pale skin, sneaking lower and brushing a small bud in the process. When Rin growled in response, Yukio gave a short chortle and just kissed him deeper. The air was being sucked out of Rin’s lungs and he felt dizzy, eyes lolling back into his head. He gasped when Yukio’s hand trailed low across his abdomen before quickly slithering into his tight pants.

“Nng-Yuk-ah!”  His brows furrowed, his lips not responding and neither did his voice. 

He grabbed hold of Yukio’s arm, not to stop him or anything, simply to edge him on one could assume. Yukio rubbed him through the thin material of his underwear, continuing with small circles to tease him and not firmly touching anything important. Rin’s nails started to cut into Yukio’s forearm but the action went unnoticed by the both of them. Yukio started to get impatient, Rin struggling against him and ass rubbing against his arousal in such a tempting way. He pulled away from Rin’s gaping mouth, brows pulled into a knot as he focused on getting Rin’s pants open.

Rin mewled into his neck, trailing his tongue along the vein that popped there whenever Yukio was yelling or seriously concentrating. Yukio swallowed when Rin took the skin into his mouth, teeth grinding against it as he sucked harshly. 

“D-Damn it.” Yukio cursed.

He let go of Rin’s hair, shifting closer to use both hands and pull the buttons and zipper loose. Why the hell did Rin even decide to sleep with jeans? He pushed the front open, giving his hand more space for…their following activities. This time, his hand crept inside Rin’s boxers, grabbing hold of a rock-hard and leaking member. Rin hissed, fangs extending and sinking into Yukio’s neck. Yukio jerked, hand involuntarily closing tighter around Rin and causing him to bite down harder. His mouth fell open, breathing heavy and rushed, and his vision blurring. He tried rubbing his eyes through his glasses, scowling and not really getting anything done. Rin knocked the glasses off, pulling back and grabbing Yukio’s shoulders. He pushed Yukio down, mouth attacking the bloody stain on the side of Yukio’s neck.

“Nnh-R-Rin, you’re l-leaving marks-ah!” Yukio grabbed hold of Rin’s hair and Rin’s fingers dug into his arms. 

Rin was seeing red, literally, suddenly blinded and driven with a burning hunger and lust pouring out of every fibre of his being. His hips thrust against Yukio’s, grip tightening even more as he growled and licked at the flowing blood. Yukio moved against him, nails digging into Rin’s skin and muscles flexing close to him. Rin sloppily kissed him with urgency, barely giving him time to breath and filling his mouth with the taste of his own blood. He was surprised at how quickly their roles switched and worried about the shit they were going to have to deal with the next day. But, now, the white heat and pulsing pleasure was way more important and for once he ignored his better sense.

“S-sorry.” Rin rasped into his mouth.

Yukio assured him that it was all right, speeding up his movements to meet up with Rin’s thrusts and raking his nails down Rin’s back. He could feel the skin tearing shallowly; causing a small spark inside him he was not familiar with. His head fell back, mouth open and the room spinning. Rin’s forehead pressed against his shoulder, calling incoherently at him. Yukio was sure he was telling him sorry and also pleading him for forgiveness after this. Yukio gave a lopsided smile, body arching one last time as Rin’s bloody mouth traced his chest. 

_Idiot, now I’ll love you even more._

\--

He was going to kill him though. He had no super healing and a shit-load of love-marks. 

**Notes for the Chapter:**

> And that's it. 
> 
> Thank you all for reading, comments & kudos!! ♥

**Author's Note:**

> Not sure where this is going. *hmmm*


End file.
